Patent GB-623537-A (GB)
Title: Improvements in or relating to electron discharge devices
IPC: H01J25/38
Filed: 1944-06-08
Abstract: 623,537. Velocity-modulated tubes. KOMPFNER, R., and WRIGHT, C. S. June 8, 1944, No. 11031. [Class 39 (i)] [Also in Group XL (c)] A " travelling-wave " electron discharge device comprises an electron gun 18, 20, Fig. 2, projecting an electron beam through a non- resonant conductor 21 capable of conveying high-frequency electrical energy from an input point 27 to an output point 29 of the device even in the absence of the electron beam and so shaped (for example as the helix shown) in relation to the beam that electric fields due to the passage of energy travel at a speed substantially equal to that of the electrons in the beam; the components of the electric field within the conductor, as is shown in Fig. 3, are mainly parallel to the beam and in operation interact continuously therewith so that beam modulation occurs and waves of a wide band of frequencies are caused by reason of such interaction to increase in amplitude as. they travel from the input point to the output point. It is suggested that the electric field in the first part of the helix interacts with the initially unmodulated beam so as to cause it to become bunched by velocity modulation, and the bunched beam thereafter travels with the wave in such phase as to deliver energy continuously to it. To avoid standing waves, both the input and output are terminated non-reflectively. The helix is supported by inward projections 22 in the vacuum envelope, outside which is a copper shell 28 forming the outer member of the transmission line, and a soft iron shield 33. A magnetic focusing coil 19 may be provided. Instead of utilizing the amplified wave, the bunched beam may be employed to produce output signals or to be deflected over the luminescent screen of an oscillograph. In a mixer, signal power is introduced into the input 114, Fig. 4, and the local oscillation 117 is introduced into the output 116 through a non-reflective attenuator 118, a slight reflection 115 being provided at the input. The bunched beam containing components at both frequencies is rectified at output electrode 111 to give an intermediate frequency component. To reduce back-coupling, the input and output systems 61, 62, Fig. 6, may be separate, the output 64 of the first system and the input 65 of the second system being connected to non- reflective terminations. Input wave applied at 63 causes the beam to leave system 61 in a bunched condition; it immediately enters system 62 and builds up an amplified wave which is taken off at 66. According to the Provisional Specification, the wave may be reflected at the output end so as to generate oscillations; the beam may be partially reflected at the collector so as to generate local oscillations and act as a mixer; in a mixer, both frequencies may be injected at the input end; by passing the beam between the helix and its outer conductor, where the fields are radial, deflection modulation may be obtained for use in amplification, oscillation or mixing, or with a fluorescent screen as an oscillograph; the helix may be replaced by a structure formed by piling apertured copper discs of equal outside diameter, but with alternately large and small internal diameters.